Pfizer’s talazoparib prolonged the time until disease progression or death in breast cancer patients with inherited BRCA mutations, compared to standard chemotherapy, in a Phase 3 trial of the treatment.
The company now plans to present the data to global health authorities with the aim of getting the treatment approved for this group of breast cancer patients, who currently have limited treatment options.
“Patients with germline BRCA-positive breast cancer are typically diagnosed at a younger age than those with non-hereditary breast cancer, and there are no therapies specifically approved for them outside of current standard of care therapies,” Jennifer Litton, MD, lead investigator of the trial, said in a press release.
Researchers presented the data at the 2017 San Antonio Breast Cancer Symposium, held Dec. 5-9.
The Phase 3 EMBRACA trial (NCT01945775) is the largest study to date examining a PARP inhibitor — a drug class targeting DNA repair processes — in patients with advanced or metastatic breast cancer and inherited BRCA mutations.
The median progression-free survival in patients treated with talazoparib in the trial was 8.6 months, which was significantly longer than the 5.6 months in patients treated with standard chemotherapy, according to their physician’s choice. This difference translated to a 46% reduction in the risk of cancer progression.
The proportion of patients responding to the treatment was more than twice as high in the talazoparib group — 62.6% of these patients responded to the treatment, compared to 27.2% in the chemotherapy group.
“EMBRACA supports the potential of talazoparib to give these patients additional time without disease progression, compared to chemotherapy,” said Litton, who is also an associate professor in the breast medical oncology department of the University of Texas MD Anderson Cancer Center.
Talazoparib is an oral drug that blocks the PARP enzyme, which acts to repair DNA damage in cells. The drug also traps the PARP enzyme at the site of DNA damage, preventing it from further DNA repair attempts.
In patients with BRCA mutations, the PARP enzyme is particularly important in the repair of DNA damage. When this enzyme is prevented from doing its job, cells — particularly fast-growing cancer cells — accumulate enough DNA damage to kill the cells.
The EMBRACA trial also demonstrated that talazoparib is effective in various patient subgroups. These included patients with triple negative (a tumor not producing estrogen, progesterone, or HER2 receptors) or hormone receptor-positive breast cancer.
It was also effective in patients with both BRCA1 and BRCA2 mutations, a history of central nervous system metastases, and in patients who were either previously untreated or previously treated with chemotherapy.
In addition, talazoparib was shown to improve the general health status and the quality of life of treated participants.
“Results from the EMBRACA study are very encouraging and a great example of precision drug development,” said Mace Rothenberg, MD, chief development officer, Oncology, Pfizer Global Product Development. “By enrolling only patients with germline BRCA-positive metastatic breast cancer, treatment with talazoparib reduced the risk of disease worsening by nearly half, compared with current standard of care chemotherapy.”
Talazoparib has also been tested in the Phase 2 ABRAZO trial (NCT02034916), which showed that patients with advanced breast cancer and inherited BRCA mutations, who had either been treated with platinum-based chemotherapy or were heavily pretreated with at least three courses of non-platinum-based chemotherapy, benefited from the treatment.